Inhaler valve mechanism

ABSTRACT

A valve mechanism is provided for use in an inhaler comprising a pressurized container, and a metering chamber, and a valve mechanism wherein the inlet and outlet valves are separate and can be operated independently. The pressure of the fluid in the canister is used to aid the opening of the outer valve so reducing the force to fire a dose. A variant of the valve mechanism allows the user to select from a range of dose volumes by appropriate orientation of the stem.

BACKGROUND OF THE INVENTION

This invention relates to inhalers and nasal sprays for medicaments orthe like and more particularly to propellant driven inhalers and nasalspray valves.

Nasal sprays and inhalers are designed to introduce medicament into thebodies of users and the distinctions between the two types of apparatusdepends on whether the medicament is introduced through the mouth or thenose of the user. However, the technology is similar in both cases andreferences to inhalers include similar, nasal spray technology.

Inhalers typically consist of a storage container and a metering valveassembly. In the valve assembly a metering volume is provided betweentwo valves. These valves are often on a single stem and act together toallow the medicament to be dispensed from the storage container, via themetering volume.

EP-A-0692434 discloses an aerosol metering valve that is designed toaddress the problem of drain back. This occurs when a dose of medicamentis left in the metering chamber over a protracted period and themedicament seeps through the seal and back into the storage container.An additional seal is introduced to close the path from the meteringchamber back into the main reservoir during a long dormant period.

U.S. Pat. No. 3,052,382 and U.S. Pat. No. 3,142,420 disclose a meteringdispenser for aerosol with fluid pressure operated piston. A cylindricalmetering chamber is provided that is sealed at either end with anelastic sealing washer.

The sequence of operation of the valve assembly generally employed ininhalers today is as follows. When the device is not in use a dose ofmedicament is stored in the metering volume and the outermost of the twovalves, which is generally a face seal, is maintained closed. The innervalve is open at this time allowing fluid communication between themetering volume and the contents of the storage container. When a doseis to be dispensed, the inner valve is first closed immediately prior tothe outer valve opening. In this way when the contents of the meteringvolume are discharged, the escape of the medicament stored in thecontainer is prevented. Dispensing is generally achieved by thecontainer being depressed within a housing, either directly by theaction of the user or by means of an operating mechanism. When themedicament has been dispensed, the valve sequence reverses as thecontainer is allowed to return to its original position and state: thusthe outer valve closes prior to the inner valve opening and the meteringvolume refills with medicament from the container. The inhaler is leftin this state until it is required again for use.

Such a dispensing cycle is a necessary feature particularly of manuallyoperated conventional devices, since the dose retained in the meteringvolume during the storage has to be dispensed immediately on demand.

Breath actuated devices currently on the market retain this valvetechnology, but in general operate by loading a spring prior toinhalation by means of some user action such as opening a mouthpiececover. This stored energy is then released automatically, to depress thepressurised container within the housing, as the patient inhales.

The advantage of breath actuated inhalers is that they eliminate theneed to coordinate the press and breathe actions of manually actuatedinhalers. As a result of this the deposition levels of the drug in thelung are not dependent on the user's coordination skills. However, thehigh force required to fire the canister gives rise to production designcompromises. Firstly, the size of the device: to fire the canistertypically requires a large spring to be fitted into the design; this canbe problematic as users prefer small discrete devices. Furthermore, thelarge firing force must be released by the small force available fromthe patient's inhalation. To achieve this requires a mechanism thatgives a high gearing of the breath force, typically 500:1. Thisgenerally has to be achieved by a multi-stage mechanism with severalcomponents resulting in a relatively complex mechanism.

A breath operated inhaler that uses the present canister valve mechanismcould be of much simpler design because it is not necessary to have asource of stored energy, for example, a large spring, to release thedose.

Generally there is a desire to make inhalers as small and discrete aspossible. The necessity for a high force spring in the device means thatsmall, thin walled components must endure high stress levels. This oftenrequires more costly, high performance polymers to be used. The problemis particularly acute in devices with dose counting. Such devicestypically require that an electrical switch is actuated, or mechanicalcounting mechanism is indexed at the point in the stroke where thecanister releases its dose. To avoid the danger of counting errors thecounting and dose release should ideally occur at the same point in thecanister stroke. For highly stressed materials, displacement due tocreep can mean that the point at which dose counting occurs drifts overthe life of the device making counting errors more likely.

The manufacture of inhalers presently on the market generally involvesassembling the inhaler and then to filling it by forcing the medicamentand propellant, either simultaneously or separately, back through thevalves and into the canister. Two problems arise from this priorconstruction and method of manufacture. The first is that the valves canbe damaged by the considerable pressure required to force them open tofill the canister. Also, there is no provision for varying the volumedispensed except by varying the concentration of the medicament suppliedto the canister.

In conventional canister valves a dose is delivered into the meteringchamber immediately after the previous dose is released. The canister isstored with the metering chamber full and the dose must be containedtherein for the time between taking one dose and the next. Inhalers, ingeneral, whether manually or breath operated, suffer from the problemthat the dose in the metering chamber can diminish over time either byescaping through the seals of the outer valve or by drain back into thestorage container if the canister is stored inverted. If the metereddose in the metering chamber leaks away, it will not refill even if thecanister is subsequently stored upright. The reduction in the dose inthe metering chamber then causes the user to receive a lower thanexpected dose at next usage.

SUMMARY OF THE INVENTION

According to the present invention there is provided a valve mechanismfor use in an inhaler comprising a pressurised container and a meteringchamber, the valve mechanism comprising:

a first valve member arranged to be positioned between the pressurisedcontainer and the metering chamber, the first valve member being movablebetween a closed position in which the container is closed, and an openposition in which the container is open to the metering chamber, thefirst valve member being biassed to remain in the first position by thepressure in the container; and

a second valve member movable between a rest position in which themetering chamber is closed, a metering position in which the valvemember actuates the opening of the first valve member to enable ametered dose of medicament to be dispensed into the metering chamber,and an open position in which the metering chamber is open to allowmedicament to be inhaled.

The three positions of the second valve facilitate the inhaler remainingempty when it is not in use and being filled only immediately prior todispensing a dose of medicament. This overcomes the problems encounteredin the prior art of the dose of medicament decaying or draining backinto the canister.

Preferably, the first valve member is further biassed to remain in thefirst position by a return spring.

The configuration of the first valve member and the metering chamberensures that the flow of aerosolised medicament into the meteringchamber is not restricted and therefore there is a reduction in problemsassociated with reliably filling the metering chamber, for example, theunwanted evaporation of propellant within the metering chamber beforethe medicament is discharged.

Preferably, the second valve member is arranged to enable the pressurein the metering chamber to assist the opening of the second valvemember.

The surface at the end of the second valve member that contacts thefirst valve member during metering of a dose, may be a cam surface or astepped surface and the first valve member has a cooperating surface bywhich the dose size can be varied.

The second valve member may include a radial seal, and wherein themovements of the first and second valve members may be independent ofone another.

Preferably, the end surface of the second valve member allows the sizeof the dose to be adjusted.

The dose size may be variable and may be user defined.

The cross-section of the first valve member may be T-shaped.

Preferably the two valves cannot be opened simultaneously.

The second valve may be breath actuated.

A valve mechanism according to the present invention may be incorporatedin an inhaler device.

An inhaler device incorporating a valve mechanism according to thepresent invention has a number of advantages over the prior art. Theprovision of a face seal between the pressurised canister and themetering chamber overcomes the problem of medicament seeping out of, orback into, the pressurised canister when the inhaler is not in use. Anadditional advantage of the face seal is that this facilitates free flowof the aerosolised medicament and propellant into the metering chamber.

Furthermore, according to the present invention there is provided amethod of manufacturing an inhaler, the method comprising the steps of:

providing a container to be pressurised closed by the first valve;

inserting medicament into the container through the first valve;

pressurising the container with propellant through the first valve; and

attaching a stem and the second valve to form the metering chamber.

The second valve may be selected from a plurality of valves withdifferent diameter stems.

The advantage of this method of manufacture is that the second valve isnot attached to the inhaler until the canister has been filled and istherefore not forced open during the filling process. The first valve isa radial seal and is therefore more resilient to the pressures involvedin the filling process than the sliding seal that comprises the secondvalve.

Furthermore, the various lines supplying the valves that form the secondvalves in the inhalers may supply valves with different stem sizes thatallow the size of the metering volume, and therefore the size of thedose to be dispensed, to be varied whilst still utilising the same firstvalve and canister and without any need to alter the concentration ofthe medicament supplied.

The operating sequence of a valve according to the present inventionensures that the dose is metered just before delivery and so resides inthe metering chamber for only a very short time. Therefore the device isstored with the metering chamber empty. Thus the problems of reductionof the metered dose seen with conventional valves are eliminated.Another advantage of the valve of the present invention is that theforce required to release a dose or the “force to fire” can be verysmall. This is achieved by dissociating the metering and firing actionsand by using the pressure of the fluid to assist the firing action.

A further advantage of the valve of the present invention is that theforce to meter a dose can be much lower than for a conventional valve.Conventional devices have radial seals as both the inner and outerseals. However, with the present valve only the outer seal needs to be aradial seal. The frictional losses of a face seal are small incomparison with those of a radial seal and this means that a weakerreturn spring can be used to keep the inner valve closed than isrequired in a conventional device with radial seals for both the innerand outer valves. The combined effect of reduced frictional losses atthe seals and a weaker inner valve return spring allows the valve of thepresent invention to meter a dose at lower force.

Furthermore, the stem component of the present invention can be added asa separate assembly operation after the rest of the device has beenassembled. This results in the possibility of a range of different stemsizes, defining different metering volumes being available based on anotherwise standard device. Thus the manufacturer can easily produce arange of product variants with different nominal dose sizes.

A further advantage of the one example of the valve of the presentinvention is that a range of dose volumes can be selected by the user byappropriate orientation of the stem.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the present invention will now be discussed with referenceto the accompanying drawings in which:

FIG. 1 a illustrates a section side view of an inhaler device accordingto the present invention;

FIG. 1 b illustrates a section side view of a valve mechanism accordingto the present invention;

FIG. 2 illustrates the detail of the valve mechanism when the cap isclosed, the so-called home position;

FIG. 3 shows the position of the valve mechanism during metering;

FIG. 4 shows the valve mechanism in the armed position;

FIG. 5 shows the valve mechanism as the trigger mechanism fires;

FIG. 6 is a schematic front view of a trigger mechanism used inconjunction with the present invention.

FIGS. 7 a to 7 c are schematic side views of the trigger mechanism invarious phases of operation; and

FIG. 8 shows a radial seal comprising the state of the art;

FIGS. 9 a to 9 c show a variant of the valve mechanism in which the usercan select between two dose sizes;

FIG. 10 shows a variant of the valve mechanism in which the user canselect from a continuously variable range of dose sizes.

FIG. 11 shows an further example of the present invention in which thestem is hollow.

FIG. 12 shows an inhaler device according to the present invention beingfilled.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an inhaler 10 in its normal, at rest, position. Theinhaler includes a pressurised container 11 having a inner valve 12.Attached to the rim 13 of the container 11 is a housing 14 within whichis contained a metering chamber 15 which incorporates part of an outervalve 16. The metering chamber 15 includes a stem 17 that allows theactuation of the inner valve 12.

The seal of the inner valve 12 is a face seal and includes a valve seat27 and a valve member 28, which has a shaft 29 and an annular flange 30to form a T-shape in cross-section. The size of the opening afforded bythe face seal allows free flow of medicament into the metering chamber15. The seal is an annular rubber seal 31 disposed between the undersideof the flange 30 and the valve seat 27 of the pressurised container 11.In this manner the seal is made primarily by the pressure of the fluidin the container 11 on the top surface of the flange 30 and by theaction of the return spring 32, which is retained by a cage 34. Thus, asthe rubber relaxes over time the seal of the present invention willretain its integrity for longer than a radial seal.

FIGS. 2 to 5 show the operation of the valve mechanism of the presentinvention. FIG. 2 shows the valve mechanism in its at rest position whenthe cap of the inhaler is closed. The inhaler remains in this positionwhenever it is not in use. The metering chamber 15 is empty and both theinner valve 12 and the outer valve 16 are closed. The outer valve 16 isa standard radial seal shuttle valve. The stem 17 is not in contact withthe inner valve 12. The advantage of using a standard radial sealshuttle valve is that the pressure in the metering chamber assists thedelivery of a dose and reduces the additional force required. The actionof these two valves results in an interlock system that prevents the twovalves from ever being opened simultaneously.

Metering of a dose of medicament is initiated by the opening of the capof the inhaler. The position of the various components at this point inthe operation of the device are shown in FIG. 3. This results in thestem 17 being pushed into contact with the inner valve 12. This in turnmoves into the pressurised container 11 and allows medicament to flowfrom the pressurised container 11 into the metering chamber 15. Theexact volume of the metering chamber 15 is defined at the moment of theclosure of the outer valve 16. It is very important that the precisevolume of the metering chamber 15 is precisely defined as this dictatesthe volume of medicament that is metered and, subsequently deliveredfrom the inhaler.

FIG. 4 shows the armed position with the cap fully open. The stem 17 islowered onto the trigger mechanism (not shown) and the inner valve 12between the metering chamber 15 and pressurised container 11 is closed.The pressure of the medicament in the metering chamber 15 forces thestem 17 down against the trigger mechanism (not shown)

In this example of the present invention the valve seal 33 of the outervalve 16 is provided by a separate rubber component in the form of anO-ring. However, in other examples it may be advantageous to use a lipseal that is either an integral part of the stem 17 or the wall of thepressurised container 11.

FIG. 5 shows a dose being dispensed. The trigger mechanism firesallowing the stem 17 to drop as a result of the pressure in the meteringchamber 15. The radial seal 33 of the valve 16 passes the exit hole 18and the dose is delivered.

FIG. 6 shows a schematic front view of the trigger mechanism in itsarmed position. This position occurs as a result of pressure in themetering chamber 15 pushing the stem 17 down on a top pivot 19. The toppivot 19 cannot move down as the middle pivot 20 is in contact with theend stop 21. Activation by the user's breath causes air to flow pastflap 22 and rotate it in an anti-clockwise direction.

FIG. 7 a also shows the trigger mechanism in its armed position. In FIG.7 b the trigger mechanism is shown moving towards the fired position.This occurs as a result of the through flow of air past the flap 22 thatmoves the middle pivot 20 away from the end stop 21. The middle pivot 20first passes the point where all pivots are co-linear. Once this pointhas been passed the top pivot 19 can move down allowing the stem 17 toextend out of the metering chamber 15 and fire a dose of medicament. Thelower flap 22 rotates anti-clockwise until it is stopped by the flapstop 23. This position is illustrated in FIG. 7 c.

To reset the trigger mechanism the flap 22 is rotated clockwise. In oneexample of the present invention this is performed by closing the cap ofthe mouthpiece. As the cap is closed the flap 22 is returned to thearmed position shown in FIG. 7 a with the middle pivot 20 against theend stop 21.

The dimensions of the valve mechanism may be chosen so that either thestem 17 may pop out as a result of the pressure on the stem 17, oralternatively must be pulled out against the friction in the outer seal33.

In the former configuration the stem diameter is around 3 mm. Thetypical frictional force with an O-ring seal is approximately 1.0 N.Typically the pressure in an inhaler aerosol is between 4 and 5 bars.The stem will by default pop out and fire the dose when the meteringchamber 15 fills. This can be used with the trigger mechanismillustrated in FIG. 7.

In the second variant the stem 17 is physically attached to the toppivot 19. This allows the linkage to pull the stem 17 down as the flap22 rotates in an anti-clockwise direction.

FIG. 8 shows a radial seal common in the art. It consists of a rubberseal 26 surrounding the stem 17 and as the stem 17 is lifted to open thevalve, the one end 24 of the bore 25 passes the seal 26 and allowsmedicament to flow through the bore 25 and leave the inhaler device.

In one variant of the design a range of dose volumes can be selected bythe user by appropriate orientation of the stem. FIG. 9 a shows avariant of the stem with a castellation feature on the top surface. Anisometric view of this feature is shown in FIG. 9 b. There is anidentical feature on the shaft 29 of the valve member 28. In oneorientation of the stem, shown in FIG. 9 a, these features interlock. Inanother orientation of the stem, shown in FIG. 9 c, these features buttup against each other. This latter configuration increases the effectivelength and volume of the metering chamber and hence the dose size thatwill be dispensed.

There are many end shapes for the stem 17 that would allow the dose sizeto be determined by the orientation of the stem. FIG. 10 gives anillustration of another possible arrangement.

The assembly process begins with the provision of pressurised containers11 fitted with a first valve 12. The container 11 is then filled withmedicament and propellant. These may be supplied together through asingle supply line or, preferably, sequentially using two differentsupply lines. The filling procedure is shown in FIG. 11. FIG. 11 showsthe lower part of the pressurised container 11 and the inner valve 12. Asupply line 35, terminating in a spigot 36 supplies the medicament tothe pressurised container 11. The spigot 36 engages with the lower faceof the valve 12 and forces the valve 12 into the container 11 therebyallowing the fluid to pass into the container 11. Once the container 11has been filled the second valve is attached. Valves with stems ofdiffering diameters can be supplied so that, using the same sizecontainer 11 and first valve 12 a number of different metering chambervolumes can be achieved.

1. A valve mechanism for use in an inhaler comprising a pressurisedcontainer and a metering chamber, the valve mechanism comprising: afirst valve member arranged to be positioned between the pressurisedcontainer and the metering chamber, the first valve member being movablebetween a closed position in which the container is closed, and an openposition in which the container is open to the metering chamber, thefirst valve member being biassed to remain in the first position by thepressure in the container; and a second valve member movable between arest position in which the metering chamber is closed, a meteringposition in which the valve member actuates the opening of the firstvalve member to enable a metered dose of medicament to be dispensed intothe metering chamber, and an open position in which the metering chamberis open to allow medicament to be inhaled.
 2. A valve mechanismaccording to claim 1 wherein the first valve member is further biassedto remain in the first position by a return spring.
 3. A valve mechanismaccording to claim 1 or claim 2, wherein the second valve member isarranged to enable the pressure in the metering chamber to assist theopening of the second valve member.
 4. A valve mechanism according toclaim 1, wherein a surface at the end of the second valve member thatcontacts the first valve member during metering of a dose, is a camsurface and the first valve member has a cooperating surface, wherebythe dose size can be varied.
 5. A valve mechanism according to claim 1,wherein a surface at the end of the second valve member that contactsthe first valve member during metering of a dose is stepped and thefirst valve member has a cooperating surface, whereby the dose size canbe varied.
 6. A valve mechanism according to claim 1, wherein the secondvalve member includes a radial seal, and wherein the movements of thefirst and second valve members are independent of one another.
 7. Avalve mechanism according to claim 1, wherein the first valve member isa face seal.
 8. A valve mechanism according to claim 4 or claim 5,wherein the end surface of the second valve member allows the size ofthe dose to be adjusted.
 9. A valve mechanism according to claim 1,wherein the cross-section of the first valve member is T-shaped.
 10. Avalve mechanism according to any of the preceding claims wherein the twovalves cannot be opened simultaneously.
 11. A valve mechanism accordingto claim 1, wherein the second valve is breath actuated.
 12. An inhalermechanism incorporating a valve mechanism according to claim 1 connectedto a pressurised container.
 13. A method of manufacturing an inhaleraccording to claim 12, the method comprising the steps of: providing acontainer to be pressurised closed by the first valve; insertingmedicament into the container through the first valve; pressurising thecontainer with propellant through the first valve; and attaching a stemand the second valve to form the metering chamber.
 14. The methodaccording to claim 9, wherein the second valve is selected from aplurality of valves with different diameter stems.